1. Field of the Invention
This invention relates to a nonvolatile semiconductor memory device including a block insulating film and a charge storage portion.
2. Background Art
There are numerous types of memory devices that are nonvolatile even during power-down if those in the research phase are included. Currently, however, nonvolatile semiconductor memory devices (flash memories) have the largest market size. Semiconductor circuits are being downscaled year by year, and semiconductor memory devices are also increasing in capacity. With regard to flash memories, which are no exception and being downscaled, application of a structure including a block insulating film and a charge storage portion, such as the MONOS (metal-oxide-nitride-oxide-silicon) structure, is under study. JP-A 2006-203200 (Kokai) discloses a technique for using an oxide containing a rare earth element and aluminum as a tunnel insulating film or a block insulating film.